The present invention relates to rechargeable electrochemical energy storage systems, and particularly relates to means for studying the operative structure and phase changes occurring within such systems comprising rechargeable cells of complementary electrodes capable of reversibly intercalating, alloying, or otherwise alternately combining with and releasing mobile ions of, e.g., sodium, potassium, or preferably lithium, in electrical energy charge and discharge operations. The invention relates, more particularly, to a rechargeable energy storage cell structure system which may be readily and reproducibly fabricated and which incorporate means for in situ study, typically under incident x-radiation, of operating cell electrode components.
The present invention in essence represents an improvement on an earlier apparatus, described in U.S. Pat. No. 5,635,138, the disclosure of which is incorporated herein by reference, for in situ x-ray study of rechargeable electrochemical cells. In that prior system, an apparatus was provided for holding, in operative relation to the transmissive window of an x-ray diffraction apparatus, a fabricated cell usually comprising a laminated assembly of positive and negative electrode members having an intervening ion-conductive, electrically insulating separator member which provided an ion-mobilizing electrolyte medium. The cell assembly commonly also comprised interlayered current collector members which provided conductive electrical connections for utilization of the cell.
Although the prior apparatus and the method of its application provided sufficiently reliable test results for the evaluation of a single cell then under examination, the extensive manipulation of cell members during the required assembly and lamination of multiple test cells, as well as the alignment of apparatus elements, contributed to an inordinate expense of time and represented a source of unpredictable test parameter variations. These disadvantages were particularly notable, for example, in the oft-practiced comparative testing of series of cells varying in minor electrode component ratio adjustments. Such lack of consistent and precisely reproducible cell assembly and test conditions have led to significant difficulties in optimizing compositions for commercial rechargeable electrochemical cells.
The present invention, on the other hand, provides a combination of proven electrochemical cell assembly and fabrication means with an x-ray capable examination component to yield a rapidly implemented, consistently reproducible test cell system. In a preferred research embodiment, this system utilizes a cell assembly comprising a conventional, widely employed Swagelok electrochemical test cell device, such as that described, for example, in U.S. Pat. Nos. 5,110,696 and 5,196,279, in combination with an x-ray transmissive cell window component of beryllium, or the like, which serves as part of an integrated hermetic enclosure for an operative rechargeable electrochemical cell. The fixed physical relationship of cell components and the ready manipulation of cell assembly members ensures rapid and economical fabrication of consistent test cells, as well as reproducible examination test results.